Opening HYSA (E*Trade vs Marcus) before temporary move to UK… any issues with access from abroad?

I’m going to be working in the UK for the next 1-3 years but ultimately plan to come back to the US (I’m a US citizen). I want to open a HYSA before I leave but have read that accessing the account from abroad can trigger a closure. Help me answer some questions!

I plan to use my parents US address and keep my US phone number. I also think I’ll basically be able to “set it and forget it”, maybe doing a new deposit a couple times a year if I have enough savings from the UK job. How worried about this should I still be?

I was planning to go with either E\*trade by Morgan Stanley or Marcus by Goldman Sachs, are either of them better in this scenario? Are the risks with moving abroad enough that you would recommend something else entirely? I like these two for the high APY and promos (E\*trade is running an offer this month and I have a referral for Marcus).

Has anyone done anything similar with either of these HYSA (or another) and successfully maintained the account from abroad?

Is all I need a VPN? Would a free VPN do the trick or do I need to pay for one? Or is it safer to just not access the account unless I’m visiting the states?

And a way more basic general HYSA question unrelated to this specific scenario: is it better for returns to put all your money in one HYSA or split it among different ones (eg to take advantage of different promos, or some other reason I’m unaware of)?